#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Software: PyCharm
# @Version : Python-
# @Author  : Shengji He
# @Email   : hsjbit@163.com
# @File    : CountCompleteTreeNodes.py
# @Time    : 2020/11/24 9:53
# @Description:


# Definition for a binary tree node.
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None


class Solution:
    def countNodes(self, root: TreeNode) -> int:
        """
        Given a complete binary tree, count the number of nodes.

        Note:

        Definition of a complete binary tree from Wikipedia:
        In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the
        last level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h.

        Example:

            Input:
                1
               / \
              2   3
             / \  /
            4  5 6

            Output: 6

        :param root:
        :return:
        """
        return 0 if not root else 1 + self.countNodes(root.left) + self.countNodes(root.right)


if __name__ == '__main__':
    print('done')
